This 2015 photo provided by Edwige Moyroud shows a Hibiscus trionum flower. The region at the base of the petals contains a dark pigment but appears blue at certain angles due to an optical effect on the surface of the cells. The color makes flowers more visible to the bees. (Edwige Moyroud via AP)

They create a blue halo. They create it to attract bees. That's what scientists reported. Flowers need bees for pollination. Bees are drawn to the color blue. But it's hard for flowers to make that color in their petals.

Some flowers use a trick. It is a trick of physics. They make a blue halo. They make it when sunlight strikes a series of tiny ridges. They are in their thin waxy surfaces. The ridges change how the light bounces back. This affects the color that one sees.

The halos appear over colored areas of a flower. People can see them over darkly colored areas. This is true if they look from certain angles.

The halo trick is uncommon among flowers. But many tulip species are among those that can do it. Some kinds of daisies and do it. And some peonies can do it. That's according to Edwige Moyroud. She works at of Cambridge University. It is in England.

Moyroud and others analyzed the flower surfaces. They used artificial flowers. They did this to show that bumblebees can see the halos. The study was published last Wednesday. It was published by the journal Nature.

An accompanying commentary said the paper shows how flowers that aren't blue can still use that color to attract bees. Further work should see whether the halo also attracts other insects, wrote Dimitri Deheyn. He is with the Scripps Institution of Oceanography. It is in La Jolla. That is in California.